ZooL.— Vol. III.] HOLMES— WEST AMERICAN CRUSTACEA. 323 



In several specimens from Point Arena, California, the 

 caudal stylets are shorter than the abdomen. This is prob- 

 ably due to the fact that the individuals were not full grown, 

 as they were all of smaller size than the type, and a careful 

 comparison of mouth parts and other structures revealed no 

 other important differences. A larger specimen taken from 

 a well in Humboldt County, California, had the caudal 

 stylets as long as those of the type. 



All the specimens examined (which had been in alcohol 

 for a long time) were of a grayish color, the segments of 

 the thorax being marked with rounded or oblong spots of a 

 lighter color. 



I have compared the type and several other specimens of 

 this species with specimens of Asellus communis Say from 

 Massachusetts, Michigan, and Illinois. The two species 

 are closely allied, but may be readily distinguished by the 

 fact that the epimera in to7nalensis are covered by the 

 thoracic segments while in communis considerable portions 

 of them are visible from above. 



The form recently described as Asellus tomalensis by 

 Miss Richardson is quite different from this species, as I 

 have determined by a re-examination of Mr. Harford's 

 type. Miss Richardson's species is much more slender, 

 the antennae longer, and the posterior segments of the 

 thorax notched instead of rounded. 



Family SPH^ROMID^. 



Sphaeroma pentodon Richardson. 



Plate XXXVII, Fig. 43- 



Head with the anterior margin bordered by a prominent raised line; 

 median frontal process small and rounded; a conspicuous groove on either 

 side in front of the eye into which the uropods are received when the animal 

 is rolled up; the distance between the anterior ends of the grooves is slightly 

 more than \ the length of the anterior margin of the head. Epistome 

 triangular, the lateral margins sinuated, the lower margin deeply concave, 

 the acute apex in contact with the median process of the front. Eyes rather 

 large, oval. Antennules reaching about to the posterior margin of the head; 

 first joint flattened and rugose anteriorly, with a small lobe at the supero- 

 proximal angle which fits into an emargination on either side of the median 



